Pneumatic cushion



Dec. '19,1922. 1,439,417.

BB. HOLMES. PNEUMATIC CUSHION. FILED JULY 3 1920.`

vINVENTOR ATTORNEYS Patented Dec. 19, 1922..'

BRADFORD B. HOLMES, or lNEW YORK',v N. Y

rnnoinafrie cusirio'n.

' Apniicauon' ined July e, i920. seriaifNo. s93,'72.

To all fw 7mm t may concern f Be it know that l, BRADFORD 1B. HoLMns,

a citizen ot the United States, residing` at NewYork, inthe county of NewYork and ,State of New York, have invented certain 'I new and useful llmproveinents in Pneumatic Cushions, or' which the following` .is a specification. i

This invention relates'to a method of regulating the load sustaining action of pneumatic cushions, and. to a cushion structure regulated by such method.

The invention is particularly suited tol motor truck suspensions and is shown eml b'oriiedin a device of this class. The struc- Ature includes auxiliary `means to cause the regulating; device to function properlyeven i att-er extreme` changes of the imposed load. There are also means to checky entr-eine movements oli-the cushion in both directions. Other features of invention relate to the proper iiunctioning of the device at the high pressures necessary in truck service, and to the securinp` ot the wide'frang'e oi" el'iective load sustainingl action called vfor by 'the' extreme variation ot sliringborne load between the empty and loaded conditions oil" the truck. A

vlVlet-allic springs, as now almost universally designed torheavy trucks must be proportioned"to sustain the maximum load, with a large factor ot' safety. `rFilis-factor o't safety, together with certainliinitations oi dimension results in unduly stiif action even under YFull load." When the truck is empty such springs practically cease to function. The present invention lprovides a pneumatic cushion which inayfeitherA be used in lieu or' a metallic spring or may be used to supplement the actionl of a metallic` spring, the pneumatic cushion beingl inherently seli regulating: as to its effectiif'eloadsustaining action., so that tulliiexibility ot the spring suspensionis had regardless of the load 'upon the truck, without lial'iility oit injury through over-compression or lrebound. l i i To secure this action l make use ot two inechanicallv related coactingil pneumatic cushions. both oi which preferably vcontain soine oil in addition'to air (or other suitable cias). Une ot these cushions operates at relatively high pressure. und is character-4 ized'by a relatively high` ratio ot' `total cushion volume to total piston displacement. The other cushion operates at relatively to piston area.

vents fbaclr iow'.

lower pressure and is characterized by 'a relatively vlower `ratio of total Cushion volume to ,total i piston displacement. Where, asin the preferred coi'istruction,` the piston strokes of the4 'two lcushions are the same, piston di`s}' laceineiit is directly Aproportional.

lIt results -from` the above leliaracteri'stics ofthe twoy cushions, that as thekt'wo' cushions are compressed by 'load shocks, the pressure in ythe low' pressure vcushion risesv far more rapidly than` that in'V the high pressure cushion, rand a point .is 'eventually reached at which thei pressure inthe lowpr`essure cushion tendsL to rise above thefpressure in the high-pressure cushion; f At/such times a check valve opens andlpermits flow of pressurefluid from the 'low pressure to 'the liiglrpressure cushion, Land thereafterl pre- Consequently, load I shocks have-the effect of increasing, the" pressure in the high pressurecushion and decreasingv lpressure, .in the low-pressure cushion,k and;

since the low-pressure'cushion has ythe la er pistony area, the effective loa(il-sustainingre,- sistancel of the two'cushions isy reducedi j Vr This results 'in4 aj lower load-sustainingr position of the two cushions.r Ahleed valve so constructed to beheld open whenever the cushion structure'is vbelow its :desired loadsustainingr position, permits `a" relaH tively slow bacle'ow yfrom the high-pressureto the low-pressure cushion whenever;

necessary to restore low-pressure cushion pressure. 'Y 'f t y Obviously this valvels held open during the compression of .thecushions by severek load shocks, but at vsuch times the low'pres sure cushion pressure is abnormally high: and any flow is towardthe high-pressure cushion. Thus keach load shock. transfers a relatively-y largre quantity of pressure Vfluid from the lowtofthe hioh ressure cushion. b

but the resulting reduction kof pressure, in

the low pressure cushion is" neutralized fin the proper degree Abya counter i'low occuir ring in the intervals between shocks, and this countei'iow is regulated by theentent and duration :of the opening ot the bleed valvef .Such opening directlycontrolledr by the average load sustaining position olf the cushion.l y i Ita truck so equipped, be runjunder heavy load and then be stopped and unloaded and again run, the cushionsv wouldbe f elongated and so stiff that practically no 52, lieetafir transfer of pressure to the high pressure cushion could occur, unless son'ie'm'eans he provided to increase the flexibility of the cushions Linder these conditions. Thisconr pensating effect l secure by using a metallic spring which opposes the' cushions, butcomes into action only when these are unduly elongated. Under such conditions the pressure fluctuations in the low pressure cushion are exaggerated by a leakage of loil from the high to the low pressure-cushiom this leakage tending to reduce the. effective volume of the low pressure cushion. The effect of this is to accelerate transfer of pressure fluid fromfthe low to the Ihigh pressure cushion, thus rapidly restoring` the cushion to normal riding position and normal flexibility.

The metallic. spring above mentioned also serves as a rebound check, its action being reinforced by an oil throttling check or retarder. Extreme load shocks are clieclredby a pneumatic dash pot, which the general organization ofl the cushion. makes it con venient to provide.

A preferred embodiment of the invention f is shown in the accompanying drawing, in

. which;

F ig. l is a vertical axial section, Fig. 2 is a plan view on a reduced scale, and

F ig. 3 is a plan view of the piston showing` the form of the valve ports.

n the drawings the side bar of a truc chassis is shown at 5 and the rear end ofa radius rod, in load bearing vrelation with 'an axle (not shown) is indicatedat 6. Liese parts merely indicate `one way of applyingy the device and are subject to mcdilication, as the spring may be used in any of various types of truck suspension.

Connected to the side bar 5 by means ofy bolts 7 is a castingl formed with an enlarged chamber 8, and with a downward extending cylindrical guideway 9. Concentric with this guide-way 9 isanopening in the top of the chamber 8. Into this opening'is threaded a cap .10,.t-he interior of which forms an eX- tension of the space within the chamber 8, and serves as a dash pot under certaiconditions of operation. The cap 10 is screwed down against a gasket 1l to secure a tight joint, and has a centraldownward projection 12, which carries the low pressure piston, housesthe bleed `valve and/certain chambers, and externally is soformed as to have a graduated throttling function.

The head 15 has a portion 17 which extends beneath the end of the radius rod 6, sufiicient clearance being allowed to permit limited movement of the parts. rlhe head 15 is further provided with a transverse channel or recess 18 which, together with a guide-way 19 in the upper face of radius rod G, confines a. thrust roller 20. By means of this the axle thrust against the radiusrod is trans ferred to head llaud excessive sidethrust on head 15 is avoided. i l

rlhreaded into the upper end of the shell y13 is a ring or annular head 2i which is designed to cooperate with a portion of the extension to produce a graduated throt`- tling action. The extension 12 is reversely tapered as indicated at 22 and 23 so that in intermediate or normal positions of the shell i3, there is virtually no throttling action, but such action increases at progressively increasing rates7` as the shell 1S approaches the limits of its movements in both directions. i

The annular space within the cap 10 and surrounding the central extension 12 is designed to receive the end of the shell 13 and theiringl, and to coact with them as a dash-pot to checlr extreme inward movement of the shell i3. To secure a smooth entrance oftheplunger into this annular' dash-pot, the lower portion of the cap 1() is formed with an internal liare as clearly shown in the drawing.` This flare, together with the taper 22, lead gradually by a progressive throttling to the more rpronounced action of the dash-pot.

rfhreaded on the lower end of the extension l2 is an annular piston head 24 which is provided with a metallic piston ring 25, causing` it vto mal-ie a relatively tight sliding` fit within the shell 13. The central portion of the piston head 24 consists of a spider 48 giving free communication to the chamber 2G formed .in the lower end of extension 12. The chamber 2G and the' space below piston 24 form the low pressure cushion chamber.

The chamber 26 cut oil" from the chainber 27 formed in the upper end of extension 12, byr a partition 28 provided with small ports 29 which are controlled by a valve 30. This valve 3() carries a sealing ring` ll which seats on an annular seat 353 surrounding the ports` 29. The valve 3h is at times unseated `by the collision of the lower end of a rod 33 connected thereto with the head 15. rllhe purpose of the spider is to guidethe rod 33. The chamber 2T' is a part of the high pressure cushion chamber within the shell t3 and is in constant con1- manication with that space by means of a port Bil. F or convenience in manufacture and assembling, access is given to the interior of chamber 2T by means of a removable screw plug 35.

The piston 24 is provided with arcuate l ports 36. arrangedinvtwo annular series, so

` that considerable area is offered to the passure cushionspace. but closing to prevent flow ina reverse direction. This valve is retained byva ring 38 having. a reversely beveled lower. face to ypermit both edges .of the' valve .to rise. `The upper side oiA ring 38 is formed with a helical spring seat kkand `an upwardlyA projecting ilange. This lseat receives andconines .the lower end of a `-lieavycoiled `spring 39. The up'perend of thisvspring willl engage the ring 21 if the cushion tends' toelOngate beyond its normal riding position, -1. e., if the shell13 nieves outward beyondfthe position shown inthe drawing; Ait-Vall othertimes thespring 39 isentirely inactive.V The' ring 33 isV held in. place by screwsd() or by any other suitable. means.

ln order toprevent y y shell 13 and guidesway 9, `a pair ofY cup v'chamber S.' Each or' these cupleatliers is leathersdl, .ll-shaped in cross section, are used, 'one .being mounted above the other yin achannel surroundingthe guide-way-9 at the junction or .this guide-Way with the spread by one of tvv-o identici-il rings 42 inserted as showin'the upper one of the ltwo rings 42 conined byA a retaining iring held by screws 14.

A suitable amount of oil may be poured in through the top ofthe cushion vby removingthe plug 35.. Air maybe pumped in under-pressure through an ali' ,valve 45..

v Thislmay ,be similar to the valve used in ypneumatic tires, andfpreferably includes a small .checlcvalve opening inward, and a cover cap. l

krlliesheet `metalniember indicated at L6 .is a dust guard-which works betweenlianges 4t? jat the forward "side ofthe. guide yentension 9, and is designedto deflect-.mud anc ydustthroivn up from the road. Y. f

Assuming that .the device .contains a `proper amountor' oil, (absolute exactnessin the amount of oilbeing by no meansessential air is A)um eed .in throuOh the .valveflx until the pressure Vin the cushion is suilicient or .preferably slightly more than .su'licient `to sustain, at the normal Ariding .position of 'the cushion, the maximum dead load toy whicli'it will be subjected.V Figure 1 shows the parts ofthe-cushion .in this normal riding` position. Y

Assume now that rthe truck is more or less.lieavilyfloaded and isdriveii over a road sufficiently rough to impart load shocks of some intensity, to the cushion. llhe ratio of the low pressure cushion space to the maxibelow: the piston mum.;displacementl of piston. 24, is rather'v low, consequently tl'iein and outmovements of ythel shell 13v and its head 15, with-reliereuce to the'v guide member 9 will produce violent pressure fluctuations in the low pres-- sure cushion space. .flhe pressure luctua tions simultaneously produced in high pres-A` sure cushion chamber 8 by, such inovei'nents `of the shell/13 will no't'be so great lbecause the area oi'l the end or' shell 13 is smalland ,this `area represents `the total piston area actingwithin the chamber 8 kand .its coinmunicating chamber. 2'7".' lConssouently the v'effect or'k load shocks on the pressure within the lowpressure cushion space is to vraise `that pressure momentarily above the pres-kv surein chamber 8. vrlhis .will produce momentary -llow of pressure Huid through fthe n y l cushion. {This .naturally ychanges the load` y leakage from chamber 8 through the sliding joint betweenthe sustaining position. of the cushion, causing theshell 13 to move inward with reference to the guide 9.v This eventually .results in the unseatingfoll valve in the periods bei tween load shoclrsand rwill vpermit pressure i l c therein. rlhe purpose oit'the chamber` 2G isv to preserrey an zur cushion space even when tue piston fl'contacts with .the surface olii thisoil, so that excess oil may be forced through the ports 36, without shocl :by efe,

.ti-eine.movements of the cushion.` Constant slow leakage of oil pastthe paclringi'ing 25 produces `a tendency 'lor oil to accumulate a tendency toincre se the violence `olfthe pressure liuotuations.v useful in. accelerat a' the regulative action in Acases whe-re the ,truclry load has been greatly red uced.y and it is necessaiyto trnnslfer con.r

side )lo pressureiluidfroni the. space be loutpiston 2% to the chamber 3 )ne function kol'ftie sprir increases lthe range ol' oscillation until tl k position .and nor.

mal flexibility. "function, except 'lo ciieckrebound.

llllien the cushion is suddenly` elongated.. there is a tendency to displace a large quan- @Thisv action is Very` rEhenthe spring. ceases to.

ico

so'tlieie isa constant f tendency to reduce ythe effective volume olE ythe low pressure cushion, and consequently,

ne resulting reductionol pressure in the lou'. pressure cushion-hasrestored the. cushion to its normal load sustaining -ilow l I entrance ot the .ring 2l into the annular tity of oil upward through the space within the ring 2l, and the coaction of thisriiig` with the tapered portion 2S otextension l2 gives a checking); action by throttling the oil Under very heavy load shocks, the

dash-pot in cap l0, gives a pronounced and rapidly increasing 'checking` action and absolutely precludes abrupt collision of the parts.

By raryingi' the relative areas or' the two cushion pistons, and by varying the relative .f'olumes et' the cushions, different Ycushion characteristics may be secured, both as to the reaction the cushion to shock and as to its rate of regulative action.

As the area ot the high pressure piston is reduced, the high pressure cushion `approaches a lined volume` reservoir in form, and function, so that this limiting case is the exact method described and claimed in my prior application, Serial No. 390,159, tiledv June i9, 1920, to which the present appli-` cation is subordinate. The method claims ot the present application are therefore restricted to regulation by the use of twoy 'cushions between which the pressure iiuid isk A transferred, this being a speciiic variant of the method oi" said yprior application. i

Having thus described my invention, what l claim is zl. That method ot controlling the resultaut load sustaining action ot' two mechanically related cushions arranged to sustain a. load conjointly and having' different eti'ective piston areas which consists in transferring' pressure fluid back and forth between the two cushions.

9.. That method oi controlling the resultant load sustaining action of two mechanically related cushions arranged to sustain a load conjointly and having different effective piston areas, which consists in eiiecting a ti'aiis'lf'er of pressure fluid back and .forth between the two cushions, by means otenergy absorbed from load shocks.y

3. That method of controlling' the resultant load sustaining action or' two mechanically related cushions `arranged to'sustain ra load conjointly and having' differentiates of pressure variation for simultaneous cushion movements under load shocks, which consists in perniittiniil a one-way flow ot pressure lluid from one cushion to the other when the pressures are differentially increased by load shocks` and controlling a reverse flow of such huid in the intervals between load shocksr according' to the load sustaining action `oi the cushions.

l. That method ot controlling the resultant load sustaining action of two mechanicall;Y related cushions arranged to sustain a load coiijoiiitly and having` different rates of pressure variation for simultaneous cushion in permitting` movements under load shocks, which consists a one-way flowk oi' pressure iluid from one cushion to the other when the pressures are differentially increased by load shocks and regulating a reverse flow of such vHuid by the load sustaining' position assumed by the cushions.

f 5. That method ot regulating the load sustaining action ot two mechanically related pneumatic cushions arranged to sustain 'a` load conjointly, crates at a cliai'acterized'4 byv arelatively high ratio of total cushion volume to cushion piston area,

one of which cushions opand the other ot which cushions operates at a relatively lower pressure and is characterized by a relatively lower ratio of total cushion yvolume to cushion piston area, which consists in permitting a relatively free vHow of pressure iiuid from the low pressure cushion to vthe high pressure cushion when cushion pressures are'i'aised by load shocks and regulating a` flow of pressure fluid from the high pressure cushion to the low pressure cushion in the intervals between load shocks. y

6. rllhat method oi regulating the load sustaining vaction of two mechanically related pneumatic cushions arranged to sustain a load conjointly, one of which cushions op-k erates ata` relatively high pressure and is` characterized by a relatively high ratio of total cushion volumev to cushion piston area,

and the other ot which cushions operates at a relatively lower pi'essure andis character- Aized by a relatively lower ratio of total cushion volume toA cushion piston area, which consists in permitting' a relatively tree tlow of pressure Afluid from thelow pressure cushion to the high pressure cushion when cushion pressures are raised by load shocks and regulatingv a i'low of pressure fluid from the high pressure cushion to the low pressure cushion in the intervals between load shocks, according to the load sustaining position assumed` by the cushions.

7. The combination with a `pneumatic cushion of the type in which cushion oscillations serve to reduce cushion pressure, and the undue shortening ofthe cushionserves to bring' about increase ot' cushion pressure, of a springr servingrto neutralize partially the load sustaining' action otl said cushion whenever said cushion unduly elongated.

8. The vcombination lwith a pneumatic cushioning' device 'oi' the type in which load shocks cause ai'eduction o'l etlective cushion pressure. oi a .spring constructed and arranged to be normally inactive but to oppose the extreme elongationy oit' said cushion incident to' substantial load reductions, whereby said cushioning' devicel is enabled to respond to load shocks and thereby reduce its load sustaining pressure in periods relativelyhigh pressure and is immediately subsequent .to such loadieductions.

9. ln a pneumatic cushioning device; the combination ol" two pneumatic cushions;"-one having ahigher ratio .of total cushion ve1- unie to' piston displacement than the other; mechanical connections between said cushions whereby they` ,operate .cenjointly; a check valve permittingl iiow from'the low ratio cushion to the high ratio cushion and closing against reverse How; and valve means controlled by the lead sustainingposition or' the cushion and serving to control a flow of pressure fluid from the high ratio cushion to the low ratio cushion.`

10. ln a pneumatic cushion device, the combination et two pneumatic cushions, one having a higher' ratio of total cushion volume to piston displacement than the other;

mechanical connections between said cushions whereby they operate conjointly; a check valve having relatively large ports permitting How lrom the low ratio cushion to the high ratio cushion and closing against reverse flow; a second valve having restricted ports connecting said cushions; and op` erativeconnections for opening and closing said second valve in different load sustaining positions of the cushions.

11. The combination with a cushion et the type containing a liquid and an expansible gas of an auxiliary throttling device serving to check the extension of said'cushion by throttling liquid flow within the cushion7 said throttling device being operative only near the opposite limits of movement of said cushion.

l2. The combination with a j pneumatic cushioning device containing a liquid and an expansible gas, oit means for producing` a flow of said liquid as the cushion elongates; and valve means Yfor controlling said flow constructed and arranged to be gradually closed as the cushion elongates beyond a desired limit.

13. The combination with a pneumatic cushioning device containing a liquid and an expansible gas, of means for producing` a flow of said liquid as the cushion elongates; valve means for controlling` said flow constructed and arranged to be gradually closed as the cushion elongates beyond a desired limit; and a metal spring positioned to resist elongation of the cushion structure beyond a normal load sustaining position.

14;. The combination with a pneumatic cushioning rdevice containing a liquid and au expansible gas, of means lior producing a `Elow of said `liquid as the cushion elongates; valve means 'tor controlling said 'ow constructed and arranged to be gradually closed as the cushion elongates beyond a desired limit; and a dash pot communicating with the space within thecushion and containing gas at the cushionpressure; said dash pot serving to check extra-ane compressive movements ot the cushion.

- l5. rlhe conibinationfoif' a casing enclosing a chamber; a tubular guide way communi'- cating t with said chan'iber;v projecting member mounted in the interior oi said casing andfprojectinginto said guide way; a lined piston head carried by said member, smaller than said guide way and concentric therewith; a tubular sleeve closed at its outer end; mounted to slide in the annular space between said guide. and said iixed piston head and making a fluid tight joint with each7 whereby two variable-volume cushion chambers are produced; a check valve permitting free unidirectional flow from one variable volume chamber to the other; and a bleed valve operated by the movements or' said tubular sleeve and controlling a communication between said variable volume chambers.

16. rlhe combination of a casing enclosing a chamber; a tubular guide way communieating with said chamber; a projecting member mounted in the interior of said casing and projecting into said guide way; a iixed piston head carried by said member; smaller than said guide way and concentric herewith; a tubular sleeve closed at its outer end; mounted to slide in the annular space between said guide and said fixed piston head and making a fluid tight joint with each.y whereby two variable volume cushion chambers are produced; a check` valve permitting tree unidirectional {iow from one variable volume chamber to the other; a bleed valve operated by the movcments ot said tubular sleeve and controlling a communication between said variable volume chambers; an annular head fast to the inner end of said sleeve and surrounding said projecting member; and a tapered lvalve portion formed on said projecting member and serving to cooperate with said surrounding` annular head; as the latter moves7 to perform a graduated throttling action.

17. The combination et a casing enclosinga chamber; a tubular guide way communieating with said chamber; a projecting member inoui'itedin the interior et said iasing and projecting into said guide way; a iixed piston head carried by said member, smaller than said guide way and concentric therewith; a tubular sleeve closed at its outer end; mounted to slide in the annular space between said guide and said Xed piston -head and making a 'Huid tight joint with each; whereby two variable volume cushion chambers are produced; a check valve permitting Ytree uudirectioi'lal tlow trom one 'ariable volume chamber to the other; a bleed valve operated by the movements et said tubular sleeve and controlling n communication between Smid variable volume (-hzunbers; :in annular houd tast to the inner end of said Sleeve and surrounding said projecting` member; o. tapered valve portion formed on said projecting member and serving to Coopera-te with said surrounding annular heed, as the latter moves, to perform a, graduated throttling action; and a spring interposed between Said fixed piston head and said annular head and serving to 10 resist undue outward movement of said sleeve.

In testimony whereof I have signed my name to this speeieation.

BRADFORD B. HOLMES. 

